1. Field of the Invention
The present invention relates, generally, to exhaust gas recirculation systems for internal combustion engines and, more specifically, to an improved exhaust gas recirculation system having an integrated valve position sensor.
2. Description of the Related Art
Exhaust gas recirculation (EGR) valves are employed to control the recirculation of a portion of the exhaust gas generated from an internal combustion engine flowing through the exhaust manifold back into the combustion chamber via the intake manifold. Recirculation of exhaust gases to the air/fuel mixture at the intake of the internal combustion engine is conducive to the reduction of the concentration of noxious nitrogen oxides in the exhaust gases which are discharged from the engine. Accordingly, and for this reason, exhaust gas recirculation is effected typically on gasoline engines when the engine is operating under part-throttle or substantial-throttle conditions. More specifically, during idling conditions, negligible amounts of nitrogen oxides are produced in the combustion chambers of the engine and, therefore, there is little or no need of recirculating exhaust gases to the air/fuel mixture. On the other hand, under part-throttle or substantial-throttle conditions, the throttle valve which controls intake air to the internal combustion engine is held in a more open position so that sufficient air may be add mixed to the fuel. At the same time, and during these operating conditions, it is common to recirculate exhaust gases into the air/fuel mixture and thereby reduce the noxious emissions of the internal combustion engine.
Diesel engines typically utilize EGR during no load (idle) through medium load. In virtually all cases, gasoline and diesel, EGR is shut off as full-load conditions are approved.
The operation of the EGR valve and thus the amount of exhaust gas recirculated is often controlled by an electrically actuated vacuum regulator (EVR) as well as a differential pressure sensor, also known as a delta pressure sensor. In turn, signals to and from these components are controlled by an engine control module (ECM). The effective control and simultaneous coordination of the various EGR components presents some difficult challenges. More specifically, it is important to precisely actuate the EGR valve so that NOx, emissions may be optimally minimized. The more components employed to effectively implement exhaust gas recirculation the longer is the system response time and the more difficult and costly it is to control the process. In the related art, the EGR valve, EVR and delta pressure sensor are typically separate components mounted at various places on the engine and interconnected via flexible or hard conduits referred to as xe2x80x9conboard plumbing.xe2x80x9d In systems presently employed in the related art, each component often requires its own mounting strategy and associated fasteners. The on-board plumbing must be routed so as not to clutter the engine. This object is not always met and EGR systems presently used in the field today can be difficult and expensive to service. Further, and because of the ever shrinking space available for the vehicle power plant, the effective use of space through efficient component packaging is a parameter which designers must constantly seek to improve.
Thus, there is a need in the art for exhaust gas recirculation systems which reduce the number of components needed to effectively recirculate exhaust gas to the air/fuel mixture. Further, there is a need for such a system that reduces the complicated on-board plumbing of the type required for vacuum actuated EGR systems. There is also a need in the art for an exhaust gas recirculation system that is easy and inexpensive to service in the field. Finally, there is a need in the art for an exhaust gas recirculation system which has improved response time and accurate repeatability and which is smaller than present systems employed in the related art.

The deficiencies in the related art are overcome by an exhaust gas recirculation system for an internal combustion engine of the present invention. The exhaust gas recirculation system includes a valve body having an exhaust port adapted for fluid communication with a source of exhaust gas, an intake port adapted for fluid communication with the intake manifold of an internal combustion engine, and a valve member. The system further includes a drive member mounted to the valve body and including a mechanical output which is rotatable in opposed first and second directions. A gear train is operatively disposed between and in meshing engagement with the rotatable mechanical output of the drive member and the valve member. More specifically, the mechanical output is rotatable in either of the first or second directions to impart linear, reciprocal motion directly to the valve member through the gear train thereby moving the valve member between opened and closed positions to control the flow of exhaust gas from the exhaust port to the intake port. In addition, the exhaust gas recirculation system further includes a sensor integrated into the valve body and operatively connected to the valve member for detecting the linear position of the valve member as it is reciprocated between its open and closed positions.
The exhaust gas recirculation system of the present invention results in elimination of a number of components found in conventional EGR systems. For example, there is no need for a vacuum regulator, diaphragm used to actuate a valve member, pressure sensor employed to sense the difference in pressure between the diaphragm and the intake manifold as well as no need for the associated on-board plumbing typically employed in connection with vacuum actuated EGR systems in the related art. Furthermore, the exhaust gas recirculation system of the present invention enjoys a much faster response when compared to vacuum actuated EGR valves and has very precise valve positioning capabilities which are highly repeatable. In addition, the exhaust gas recirculation system of the present invention is relatively small and compact and therefore has improved xe2x80x9cpackagingxe2x80x9d characteristics allowing engine designers greater freedom when positioning the EGR system of the present invention relative to other related engine components.
Other objects, features and advantages of the present invention will be readily appreciated as the same becomes better understood after reading the subsequent description taken in connection with the accompanying drawings.